Stabilized vinyl chloride polymer compositions

Abstract

The heat stability imparted to vinyl polymers by a given concentration of certain sulfur-containing organotin compounds is not adversely affected with respect to either long term stability or delay in appearance of initial discoloration when a portion of the sulfur-containing organotin compound is replaced by certain less effective organotin stabilizers, including tetraorganotin compounds and diorganotin carboxylates.

What is claimed is: 
     
       1. An improved two-component heat stabilizer for vinyl chloride polymers, said stabilizer consisting essentially of a sulfur-containing organotin compound and a non-sulfur-containing organotin compound, the weight ratio of the sulfur-containing compound to the non-sulfur-containing compound being between 4:1 and 1:4, respectively, wherein the sulfur-containing organotin compound exhibits a formula selected ##EQU7## and the non-sulfur-containing organotin compound exhibits a formula selected from the group consisting of R 2   4  R 2   5  Sn, R 3   4  R 5  Sn and ##EQU8## wherein R 1  and R 2  are individually selected from the group consisting of alkyl radicals containing between 1 and 20 carbon atoms, cycloalkyl, aryl, alkaryl and aralkyl radicals, R 3  is a methylene or ethylene radical, R 4  and R 5  are selected from the same group as R 1 , with the proviso that R 4  and R 5  are not identical when both are bonded directly to a tin atom and a represents the integer 1 or 2. 
     
     
       2. The improved two-component heat stabilizer of claim 1 wherein the non-sulfur-containing organotin compound is selected from the group consisting of tetraorganotin compounds of the general formulae R 2   4  R 2   5  Sn and R 3   4  R 5  Sn wherein R 4  is butyl or octyl and R 5  is phenyl. 
     
     
       3. The improved two-component heat stabilizer of claim 1 wherein the weight ratio of sulfur-containing organotin compound to non-sulfur-containing organotin compound is between 2:1 and 1:2 respectively. 
     
     
       4. An improved heat stabilized vinyl chloride polymer composition wherein the polymer is selected from the group consisting of vinyl chloride homopolymers and copolymers of vinyl chloride with up to 50 mole percent, based on total monomers, of an ethylenically unsaturated monomer that is copolymerizable with vinyl chloride, said composition containing between 0.2 and 20 parts per 100 parts by weight of vinyl chloride polymer, of a stabilizer consisting essentially of a sulfur-containing organotin compound and a non-sulfur containing organotin compound, the weight ratio of the sulfur-containing organotin compound to the non-sulfur-containing organotin compound being between 4:1 and 1:4, respectively, wherein the sulfur-containing organotin compound exhibits a formula selected from the group consisting of R a   1  Sn(SR 2 ) 4   -a , ##EQU9## and the non-sulfur-containing organotin compound exhibits a formula selected from the group consisting of R 2   4  R 2   5  Sn, R 3   4  R 5  Sn and ##EQU10## wherein R 1  and R 2  are individually selected from the group consisting of alkyl radicals containing between 1 and 20 carbon atoms, cycloalkyl, aryl, alkaryl and aralkyl radicals, R 3  is a methylene or ethylene radical, R 4  and R 5  are selected from the same group as R 1 , with the proviso that R 4  and R 5  are not identical when both are bonded directly to a tin atom and a represents the integer 1 or 2. 
     
     
       5. The improved heat stabilized vinyl chloride polymer composition of claim 4 wherein the non-sulfur-containing organotin compound is selected from the group consisting of tetraorganotin compounds of the general formulae R 2   4  R 2   5  Sn and R 3   4  R 5  Sn wherein R 4  is butyl or octyl and R 5  is phenyl. 
     
     
       6. The improved heat stabilized vinyl chloride polymer composition of claim 4 wherein the weight ratio of sulfur-containing organotin compound to non-sulfur-containing organotin compound is between 2:1 and 1:2 respectively, and the total stabilizer concentration is between 1.5 and 3 parts by weight per 100 parts of vinyl chloride polymer.